A display device includes a self-light emitting display device and a non-light emitting display device. A liquid crystal display device is the most representative non-light emitting display device. A driving method of liquid crystal in a liquid crystal display device includes a vertical electric field type in which voltage is applied vertically to a substrate and a horizontal electrical field type in which voltage is applied almost parallel to the substrate.
In recent years, a liquid crystal display device has attracted attention, in which voltage is applied to generate an electric field in a horizontal direction (a direction parallel to a substrate), and a liquid crystal molecule rotates parallel to a substrate plane to make light from a backlight transmit or not transmit, thereby displaying an image (for example, see Patent Document 1: Japanese Published Patent Application No. H9-105918 and Non Patent Document 1: Ultra-FFS TFT-LCD with Super Image Quality and Fast Response Time 2001 SID pp. 484-487).
Each of the vertical electric field type and the horizontal electric field type has an advantage and a disadvantage. For example, the horizontal electrical field type has characteristics such as a wide viewing angle, high contrast, high gradation display, and the like compared to the vertical electric field type typified by a TN type, and is used as a monitor or television. These kinds of liquid crystal display devices coexist in a field of liquid crystal, and products have been developed. In addition, each of a liquid crystal material for a horizontal electric field type and a liquid crystal material for a vertical electric field type has been developed and has different material characteristics in accordance with a direction of applied voltage.
Further, a horizontal electric field liquid crystal display device includes an IPS (In-Plane Switching) type and an FFS (Fringe Field Switching) type. In an IPS type, a pixel electrode having a comb-shape or a slit and a common electrode having a comb-shape or a slit are alternately arranged, and an electric field almost parallel to a substrate is generated between the pixel electrode and the common electrode, thereby driving a liquid crystal display device. On the other hand, in an FFS type, a pixel electrode having a comb-shape or a slit is arranged over a common electrode which has a planar shape and is entirely formed in a pixel portion. An electric field almost parallel to a substrate is generated between the pixel electrode and the common electrode, thereby driving a liquid crystal display device.
In such a kind of liquid crystal display device, there are advantages such as a wide viewing angle and less color-shift depending on an angle at which a display screen is seen, and the liquid crystal display device is effectively used in a display portion of a TV set.
A transmission type liquid crystal display device which utilizes light from a backlight has a problem in that, although a display image is easily seen in a dark room, a display image is not easily seen in sunlight. In particular, this problem greatly influences an electronic appliance which is often used outdoors, such as a camera, a mobile information terminal, or a mobile phone.
Therefore, a liquid crystal display device which can display a favorable image both indoors and outdoors and has a wide viewing angle is expected to be developed.